The present invention relates to the field of the treatment and prevention of neurological diseases, in particular associated with neurological lesions linked in particular to the phenomenon of excitotoxicity. It relates more particularly to a novel therapeutic application of (S)-roscovitine, the chemical name of which is 6(benzylamino)2(S) [[hydroxymethyl)propyl]amino]-9-isopropylpurine).
Excitotoxicity corresponds to an accumulation of excitatory amino acids that excessively activate the glutamate receptors leading to neurone death (Olney J W and Ishimaru M J, 1999; Excitotoxic cell death. Cell death and diseases of the nervous system, Humana Press Inc: 197-219). Excitatory amino acids represent a group of structural analogues of glutamate comprising numerous members including aspartate, kainate and some of its derivatives, known to represent powerful neurone exciters. Glutamate is indisputably the best characterised excitatory amino acid. The effect of excitatory amino acids is transmitted by the metabotropic and ionotropic glutamate receptors of the NMDA, AMPA and kainate type.
Excitotoxicity thus plays a major role in the development of neurological lesions associated with numerous neurological diseases, in particular acute and chronic neurological diseases. (Choi, 1988, Trends Neurosci, vol 11, pages 465-459; Coyle and Puttfarcken, 1993, Science, vol. 262, pages 689-695; Lipton and Rosenberg, 1994, New Engl J Med, vol. 330, pages 613-622). It is therefore advantageous to identify and characterise neuroprotective compounds for preventing and/or treating neurological lesions in particular relating to the phenomenon of excitotoxity.
The use of the R isomer and the racemic mixture of roscovitine in the treatment of neurone apoptosis has been described previously in European patent EP 0 874 847. This patent reveals the anti-mitotic properties of roscovitine and in particular its inhibitory action on various cyclin-dependent kinase (cdk) proteins involved in the cell division cycle or apoptosis. On the basis of the results, and relying on the known relationships between the cell division cycle and apoptosis (Vermeulen et al, Cell Prolif. 2003 vol. 36(3), pages 131-49), the authors of this patent have suggested a possible effect of roscovitine on neurone apoptosis. Although some compounds are already used for treating neurological lesions, they may have side effects, such as a certain toxicity or insufficient efficacy. Therefore, there remains a need for compounds having improved properties for treating neurological lesions.
Surprisingly, the inventors have discovered that the S isomer of roscovitine makes it possible to wholly or partially resolve the above-mentioned deficiencies, and that it has a better neuroprotective efficacy than the R isomer. Thus the inventors have now identified and characterised a particular compound, (S)-roscovitine, for effectively preventing and/or treating neurological lesions linked in particular to the phenomenon of excitotoxity. This neuroprotective effect of (S)-roscovitine is particularly unexpected. Specifically, (S)-roscovitine inhibits various cyclin-dependent kinase (cdk) proteins involved in the cell division cycle or apoptosis more weakly than (R)-roscovitine. In particular, the inhibitory activity of (S)-roscovitine on cdk-5, cdk-1/cyclin B and cdc2/cyclin B kinase proteins is lower than that of (R)-roscovitine (De Azevedo et al., Eur. J. Biochem. 243, 518-526, 1997; Bach et al, The Journal of Biochemical Chemistry, 280, 35, 31208-31219). Incidentally, these kinase proteins, in particular cdk-5 and cdc2/cyclin B, are known for their role in neurone death (Dhavan and Tsai, 2001; Busser et al. 1998).
According to a first aspect, an object of the invention is the use of (S)-roscovitine or 6-(benzyl-amino)-2(S)-[[1-(hydroxymethyl)propyl]amino]-9-isopropylpurine) or at least one of its pharmaceutically acceptable salts for manufacturing a medication intended for the prevention and/or treatment of neurological diseases. “(S)-roscovitine” refers to the compound of the following formula:
6-(benzyl-amino)-2(S)-[[1-hydroxymethyl)propyl]amino]-9-isopropylpurine), in particular in an enantiomeric excess greater than or equal to 90%, in particular greater than or equal to 95%, especially greater than or equal to 99%, or even greater than or equal to 99.5%.
The enantiomeric excess can be defined by the formula ((S)-roscovitine−(R)-roscovitine/(S)-roscovitine+(R)-roscovitine)×100.
(S)-roscovitine can be obtained according to methods well known to persons skilled in the art, for example by a three-step synthesis from 2,6-dichloropurine as described by Havlicek et al (J. Med. Chem, 1997, 40, 408) and by Wang et al (Tetrahefron: Asymmetry, 2001, 12, 2891). (S)-roscovitine is also available from Alexis Corporation under reference No ALX-350-293-M001. “Pharmaceutically acceptable salts” refers to salts suitable for pharmaceutical use. Examples of pharmaceutically acceptable salts include benzene sulfonate, bromhydrate, chlorhydrate, citrate, ethanesulfonate, fumarate, gluconate, iodate, isethionate, maleate, methanesulfonate, methylene-bis-b-oxynaphthoate, nitrate, oxalate, pamoate, phosphate, salicylate, succinate, sulphate, tartrate, theophyllinacetate and p-toluenesulfate. The pharmaceutically acceptable salts of (S)-roscovitine can be obtained by methods well known to persons skilled in the art.
Generally “neurological disease” refers to a disease characterised by “neurological lesions”. “Neurological lesions” refers to a structural alteration in the nervous system in its anatomical and physiological characteristics. The lesion may be microscopic or macroscopic. The lesion may be of traumatic origin or caused by a disease, in particular by acute or chronic neurological diseases. These neurological lesions may affect various cell types, neurones, astrocytes, oligodendrocytes, microglia and progenitors of these cells.
In some cases, the neurological lesions are linked to the phenomenon of excitotoxicity.
In particular, the prevention and/or treatment of neurological lesions is associated with the neuroprotection activity of (S)-roscovitine. “Neuroprotection” refers to the ability of a compound to prevent the death of healthy and/or ailing neural cells. Neural cells refer to the cells of the nervous system and in particular of the brain. These neural cells may in particular be chosen from neurones, astrocytes and oligodendrocytes.
Neuroprotection is particularly advantageous in the case of neurological ailments, in particular acute or chronic neurological ailments. Specifically, these ailments may be associated with neural cell degeneration leading to cell death. This may thus make it possible the use of compounds for preventing and/or delaying the death of these neural cells, or at least some of these neural cells, healthy and/or ailing. For example, after a stroke some neural cells die immediately, or almost immediately, thereby defining a so-called “necrotic core”. However, there also exists a so-called “penumbra” zone, juxtaposing the necrotic core, in which the cells may be progressively affected before reaching cell death. The use of certain neuroprotective therapeutic agents may prevent the process of at least some of these cells towards neural death.
According to a particular embodiment of the use according to the invention, the neurological diseases are chronic neurological diseases. “Chronic neurological diseases” refer to neurological diseases the symptoms of which may be initially slight but which may progressively develop and worsen, for example over several years.
Among chronic neurological diseases the following can be cited:
neurodegenerative diseases (Adams and Victor; Third edition; McGraw-Hill book company; 1995) comprising:
diseases with extrapyramidal syndrome, in particular Parkinson's disease, progressive supranuclear paralysis (Steel-Richardson and Olzewski syndromes), multiple system atrophy and striatonigral degeneration;
dementias, in particular Alzheimer's disease, vascular dementias, Lewy body disease, frontotemporal dementias, cortico-basal degeneration and Huntington's chorea, and
other neurodegenerative diseases, in particular amyotrophic lateral sclerosis and Creutzfeld-Jakob disease (Choi, 1988; Coyle and Puttfarcken, 1993; Lipton and Rosenberg, 1994);
demyelinating diseases, in particular multiple sclerosis, disseminated acute allergic encephalitis, Devic's disease (neuromyelitis optica) and genetic diseases with affliction of the myelin, in particular Pelizaeus-Merzbacher disease.
According to another particular embodiment, neurological diseases are acute neurological diseases, in particular ischemic cerebral vascular accident.
“Acute neurological diseases” refer to neurological diseases the symptoms and clinical signs of which may initially be very marked and may stabilise rapidly, for example after a few days. Acute neurological diseases comprise:
epilepsy;
status epilepticus;
stroke, in particular ischemic;
cerebral haemorrhages;
cerebral hypoxia during cardiac arrests;
cranial traumatisms, and
neurological diseases causing focal and/or global cerebral hypoxia, occurring in particular during extracorporeal circulations, in particular during cardiac and/or vascular interventions and carotid surgery.
Cerebral haemorrhages refer to intraparenchymatous haemorrhages and meningeal haemorrhages. After meningeal haemorrhage an ischemia may occur in relation to the vasospasm. (S)-roscovitine could prevent or reduce cerebral ischemia following a meningeal haemorrhage.
In particular, certain cerebral haemorrhages may be linked to the use of a thrombolytic agent, in particular tissue plasminogen activator (t-PA). Specifically, thrombolytic agents used in the first hours of an ischemic stroke may cause cerebral haemorrhages. These cerebral haemorrhages represent a major side effect of thrombolosis during ischemic accident. (S)-roscovitine could therefore be advantageous in association with a thrombolytic agent for reducing the risk of occurrence of a cerebral haemorrhage by protecting the haematoencephalic barrier. (S)-roscovitine could act as an anti-aptopic agent in cerebral endothelial cells. Cerebral endothelial cells are one of the major components of the haematoencephalic barrier.
The medication according to the invention may further comprise at least one anti-neurodegenerative agent, in particular an agent intended for combating and/or preventing chronic and/or acute neurological disease and more particularly ischemic stroke. “Anti-neurodegenerative agent” refers to a compound for combating and/or preventing nervous system degeneration. Examples of anti-neurodegenerative agent include acetylcholinesterase inhibitors such as donepazil, selegiline, rivastigmine and galantamine, and antiglutamatergics such as memantine and riluzole. Thus, (S)-roscovitine can be used in association with an anticholinesterasic medication (donepezil, rivastigmine, galantamine) or an antiglutamatergic medication (memantine) for Alzheimer's disease or other dementias, such as vascular dementia, Lewy body disease, fronto-temporal dementias, cortico-basal degeneration, Huntington's chorea or Parkinsonian dementia . . . . (S)-roscovitine could be used in association with riluzole for amyotrophic lateral sclerosis.
(S)-roscovitine and the anti-neurodegenerative agent can be administered simultaneously, separately or staged over time. (S)-roscovitine and the anti-neurodegenerative agent can be present in the medication according to the invention in a molar ratio ranging from 10/1 to 1/10.
The medication according the invention can further comprise at least one thrombolytic agent. “Thrombolytic agent” refers to a substance capable of lysing blood clots, such as tissue plasminogen activator (t-PA), streptokinase, urokinase and desmoteplase. (S)-roscovitine and the thrombolytic agent can be administered simultaneously, separately or staged over time. (S)-roscovitine and the thrombolytic agent can be present in the medication according to the invention in a molar ratio ranging from 100/1 to 1/100.
Thrombolytic agents may have side effects. They may for example cause cerebral haemorrhages. The use of (S)-roscovitine in combination with at least one thrombolytic agent, in particular t-PA, may reduce some of these side effects, and in particular the risk of cerebral haemorrhage.
The medication according to the invention may further comprise at least one platelet aggregation inhibiting agent. Examples of “platelet aggregation inhibiting agent” include acetylsalicylic acid, ticlopidine hydrochlorate, clopidogrel, dipyridamole, abciximab and flurbiprofen. (S)-roscovitine can be used in combination with a platelet aggregation inhibiting agent for ischemic stroke. (S)-roscovitine and the platelet aggregation inhibiting agent can be administered simultaneously, separately or staged over time. (S)-roscovitine and the platelet aggregation inhibiting agent can be present in the medication according to the invention in a molar ratio ranging from 10/1 to 1/10.
The medications according to the invention can be administered by different routes. For example, administration methods that can be used for the medications according to the invention include, oral, rectal, cutaneous, pulmonary, nasal, sublingual and parenteral administration, in particular intradermic, subcutaneous, intramuscular, intravenous, intra-arterial, intrarachidian, intra-articular, intrapleural and intraperitoneal administration. In particular, when the neurological diseases are acute neurological diseases, the preferred administration routes for the medications according to the invention are intravenous, intramuscular, sublingual and cutaneous administration, preferably intravenous and intramuscular administration and, most preferably, intravenous administration. In particular, when the neurological diseases are chronic neurological diseases, the preferred administration route for the medications according to the invention is oral administration. The medications according to the invention can be administered one or more times or in continuous release, in particular in continuous perfusion.
The medications according to the invention can be in different forms, in particular in a form chosen from the group comprising tablets, capsules, pills, syrups, suspensions, solutions, powders, granules, emulsions, microspheres and injectable solutions, preferably tablets, injectable solutions, sublingual sprays and skin patches. These various forms can be obtained by methods well known to persons skilled in the art. The formulations suitable for parenteral administration, the pharmaceutically acceptable vehicles suitable for this administration route and the corresponding formulation and administration techniques can be implemented according to methods well known to persons skilled in the art, in particular those described in the manual Remington's Pharmaceutical Sciences (Mack Publishing Co., Easton, Pa., 20th edition, 2000).
According to another particular embodiment, 6-(benzyl-amino)-2(S)-[[1-(hydroxymethyl)propyl]amino]-9-isopropylpurine) or at least one of its pharmaceutically acceptable salts is present in the medication in a quantity ranging from 50 mg to 5 g per unit dose, in particular 100 mg to 2 g. The medication according to the invention can be administered in one or more doses per day, preferably in 1 to 4 doses per day. Advantageously, (S)-roscovitine can be administered in a quantity ranging from 1 to 200 mg/kg per day. Advantageously, the medication comprises a quantity of 6-(benzyl-amino)-2(S)-[[1-(hydroxymethyl)propyl]amino]-9-isopropylpurine) or at least one of its pharmaceutically acceptable salts ranging from 50 mg to 5 g.
According to another particular embodiment of the use according to the invention, the medication further comprises a pharmaceutically acceptable carrier. “Pharmaceutically acceptable carrier” refers to any material that is suitable for use in a pharmaceutical product. For example, pharmaceutically acceptable carriers include lactose, starch, optionally modified, cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, mannitol, sorbitol, xylitol, dextrose, calcium sulphate, calcium phosphate, calcium lactate, dextrates, inositol, calcium carbonate, glycin, bentonite, polyvynylpyrrolidone and mixtures thereof. The medication according to the invention can comprise a proportion of pharmaceutically acceptable carrier ranging from 5% to 99% by weight, especially 10% to 90% by weight, and in particular 20% to 75% by weight with respect to the total weight of the composition. Other advantages and features of the invention will become apparent from the figures and examples that follow.